gchq/CyberChef · warning · OperationError

Invalid key length, required to be integer.

Error message

Invalid key length, required to be integer.

What it means

Third validation in Generate De Bruijn Sequence: requires key length `n` to be an integer. Catches fractional n (e.g. 3.5) since the recursion and array sizing assume a whole count of symbol positions. NaN/Infinity are also rejected.

Source

Thrown at src/core/operations/GenerateDeBruijnSequence.mjs:58

    /**
     * @param {string} input
     * @param {Object[]} args
     * @returns {string}
     */
    run(input, args) {
        const [k, n] = args;

        if (k < 2 || k > 9) {
            throw new OperationError("Invalid alphabet size, required to be between 2 and 9 (inclusive).");
        }

        if (!Number.isInteger(k)) {
            throw new OperationError("Invalid alphabet size, required to be integer.");
        }

        if (!Number.isInteger(n)) {
            throw new OperationError("Invalid key length, required to be integer.");
        }

        if (n < 2) {
            throw new OperationError("Invalid key length, required to be at least 2.");
        }

        if (Math.pow(k, n) > 50000) {
            throw new OperationError("Too many permutations, please reduce k^n to under 50,000.");
        }

        const a = new Array(k * n).fill(0);
        const sequence = [];

        (function db(t = 1, p = 1) {
            if (t > n) {
                if (n % p !== 0) return;
                for (let j = 1; j <= p; j++) {
                    sequence.push(a[j]);

View on GitHub (pinned to 4290ea7539)

Solutions

1. Round n to a whole number.
2. Enter only integers in the Key length field.
3. Wrap computed n with Math.round/Math.floor.

Example fix

// before
args = [2, 3.5];
// after
args = [2, 4];

if (!Number.isInteger(n)) throw new Error("Key length n must be an integer");

function isInt(n){return Number.isInteger(n);}

When it happens

Trigger: Entering a decimal key length like 3.5; a computed float passed programmatically without rounding.

Common situations: Number field accepting decimals; scripting with an unrounded computed value.

Related errors

• Invalid alphabet size, required to be integer.
• Invalid alphabet size, required to be between 2 and 9 (inclu
• Invalid key length, required to be at least 2.
• Too many permutations, please reduce k^n to under 50,000.
• Invalid block cipher mode: ${mode}

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/6a386992e9ce1d38. Report an issue: GitHub.